1. Field of the Invention
The present invention relates to a plating apparatus and a plating liquid removing method, and more particularly to a plating apparatus useful for filling a metal such as copper into recesses for interconnects formed in a semiconductor substrate, and a method for removing plating liquid remaining on a substrate-contacting portion, or portions in its vicinity, of a substrate holding member for use in the plating apparatus.
2. Description of the Related Art
Generally, aluminum or aluminum alloy has been used as a material for forming interconnect circuits on a surface of a semiconductor substrate. Higher integrated density on the semiconductor substrate requires that a material having a higher electric conductivity should be used for interconnect circuits. Therefore, there has been proposed a method comprising plating a surface of a substrate to fill interconnect patterns, formed in the substrate, with copper or a copper alloy.
Various methods such as chemical vapor deposition (CVD) process, sputtering process, and the like have been used to fill interconnect patterns, formed in a substrate, with copper or a copper alloy. However, when a metallic layer on a substrate is formed of copper or a copper alloy, i.e., when copper interconnects are formed on the substrate, the CVD process requires high cost, and, if an aspect ratio is high (i.e., a depth of the pattern is larger than a width thereof), then it is difficult to fill the interconnect patterns with copper or a copper alloy during a sputtering process. Therefore, the aforementioned plating method is most effective to fill interconnect patterns, formed in a substrate, with copper or a copper alloy.
There are various methods for plating a surface of a semiconductor substrate with copper. For example, in a cup-type plating method, a dip-type plating method, or the like, a plating tank always holds a plating liquid, and a substrate is dipped into the plating liquid. In another plating method, a plating tank holds a plating liquid only when a substrate is fed into a plating container. Further, in an electrolytic plating method, an electric potential difference is applied to plate a substrate. On the other hand, in an electroless plating method, an electric potential difference is not applied.
In cup-type plating apparatuses, a substrate is held by a substrate holding member with a peripheral edge and a back surface of the substrate being sealed, and plating is performed by contacting an exposed front surface of the substrate with a plating liquid. After this plating treatment, plating liquid is likely to remain on a substrate-contacting portion, or portions in its vicinity, of a substrate holding member. This remaining plating liquid, when dried, can produce undesired particles. Moreover, the remaining plating liquid can adhere to a subsequent substrate to be plated, leading to an insufficient plating of this substrate.
A method has been developed for removing such a plating liquid remaining on the substrate-contacting portion, or portions in its vicinity, of a substrate holding member. According to this method, a plating liquid removing device, having an absorbent for absorbing a plating liquid, or a sucking tool for sucking a plating liquid, is allowed to move in a circumferential direction along the substrate-contacting portion, or portions in its vicinity, of a substrate holding member so as to remove by absorption or suction plating liquid remaining on the substrate-contacting portion or portions in its vicinity.
The above conventional plating apparatuses that carry out this method, however, have the following drawbacks. The conventional apparatuses are so designed that the substrate holding member is fixed stationarily while the plating liquid removing device is allowed to rotate. This makes it impossible to conduct dewatering (spin-drying) of the substrate-contacting portion, or portions in its vicinity, of the substrate holding member. Since a large quantity of plating liquid thus remains, it is necessary to conduct a plating liquid removing operation for every plating treatment. Moreover, each plating liquid removing operation requires a considerably long time. Furthermore, removal of the large a quantity of plating liquid leads to consumption of an increased amount of plating liquid, resulting in an increased production cost.